Against the backdrop of global warming and exhaustion of fossil resources, production of chemical products using renewable resources, along with production of biofuels, is recognized as an emerging industry, biorefinery, which is an important means for realizing a low-carbon society, and has attracted keen attention.
Aniline is widely used as raw materials for various products including chemical products, such as dyes and rubber product materials (a vulcanization accelerator and an antioxidant for tires, etc.); functional materials, such as and textiles and conductive polymers; agricultural chemicals; medicinal drugs; or the like.
Currently, aniline is chemically produced from crude oil as a raw material. Chemical processes for producing aniline include a process in which nitrobenzen is reduced with the use of tin or iron and hydrochloric acid; a process in which nitrobenzen is reduced by hydrogen addition with the use of a metal catalyst, such as copper or nickel; and a process called ammonolysis, in which chlorobenzene and ammonia are made to react at high temperature and pressure. They are all typical energy-consumptive processes in the chemical industry requiring great amounts of solvent and thermal energy. Therefore, in the light of global environment conservation and greenhouse gas reduction, there is an urgent need to develop an environment-conscious, energy saving process that allows production of aniline from renewable resources and can reduce carbon dioxide emissions and waste products, that is, to establish bioaniline production technologies.
However, production of bioaniline from renewable resources is less productive as compared to production of lactic acid or ethanol because the metabolic reaction from a raw material sugar consists of a great many steps. In addition, there are problems, such as inhibition of bacterial growth by produced aniline and cytotoxicity of aniline. Therefore, industrial production of aniline has been considered to be impossible.
Specifically known examples of technologies for producing aniline are as follows.
For example, Non Patent Literature 1 discloses that a slight amount of aniline is produced by culturing Mycobacterium smegmatis, washing the cells, and then adding 4-aminobenzoic acid. However, the process of Non Patent Literature 1 does not show practically sufficient aniline productivity. Non Patent Literature 1 does not mention any enzyme involved in aniline production from 4-aminobenzoic acid, let alone its activity or related gene.
Non Patent Literature 2 discloses that a slight amount of aniline is produced by adding anthranilic acid (2-aminobenzoic acid) or 4-aminobenzoic acid to washed cells of virulent Escherichia coli 0111 or an extract from the cells. However, the process of Non Patent Literature 2 does not have practically sufficient aniline productivity. Non Patent Literature 2 does not mention any enzyme involved in aniline production from 4-aminobenzoic acid, let alone its activity or related gene.
Patent Literature 1 discloses a technology in which Streptomyces griseus is cultured in TSB culture medium (Trypticase Soy Broth) supplemented with glucose (raw material for aniline) under aerobic conditions for 4 to 5 days for aniline production. However, Patent Literature 1 does not specifically show the amount of produced aniline or the productivity. Therefore, the practicality of the method of Patent Literature 1 is unknown.